Macroscopic concepts pertaining to the Unruh effect are introduced in order to clarify its physical manifestations. It is explained why, from a macroscopic perspective, an accelerated observer will not register any global thermal effects of acceleration in the inertial (Minkowskian) vacuum state. This result is not in conflict with the well–known fact that microscopic probes respond non–trivially to acceleration if coupled to the vacuum. But this response cannot be interpreted as the result of heat which is transferred from a heat bath surrounding the observer.

IHES, Goettingen